The Magellanic Stream is a 100 \arcdeg \times 10 \arcdeg filament of gas which lies within the Galactic halo and contains \sim 2 \times 10 ^ { 8 } { M } _ { \odot } of neutral hydrogen .
In this paper we present data from the HI Parkes All Sky Survey ( HIPASS ) in the first complete survey of the entire Magellanic Stream and its surroundings .
We also present a summary of the reprocessing techniques used to recover large-scale structure in the Stream .
The substantial improvement in spatial resolution and angular coverage compared to previous surveys reveals a variety of prominent features , including : bifurcation along the main Stream filament ; dense , isolated clouds which follow the entire length of the Stream ; head-tail structures ; and a complex filamentary web at the head of the Stream where gas is being freshly stripped away from the Small Magellanic Cloud and the Bridge .
Debris which appears to be of Magellanic origin extends out to 20° from the main Stream filaments .
The Magellanic Stream has a velocity gradient of 700 km s ^ { -1 } from the Clouds to the tail of the Stream , \sim 390 km s ^ { -1 } greater than that due to Galactic rotation alone , therefore implying a non-circular orbit .
The dual filaments comprising the Stream are likely to be relics from gas stripped separately from the Magellanic Bridge and the SMC .
This implies : ( a ) the Bridge is somewhat older than conventionally assumed ; and ( b ) the Clouds have been bound together for at least one or two orbits .
The transverse velocity gradient of the Stream also appears to support long-term binary motion of the Clouds .
A significant number of the most elongated cataloged Stream clouds ( containing \sim 1 % of the Stream mass ) have position angles aligned along the Stream .
This suggests the presence of shearing motions within the Stream , arising from tidal forces or interaction with the tenuous Galactic halo .
As previously noted , clouds within one region of the Stream , along the sightline to the less distant half ( southern half on the sky ) of the Sculptor Group , show anomalous properties .
There are more clouds along this sightline than any other part of the Stream and their velocity distribution significantly deviates from the gradient along the Stream .
We argue that this deviation could be due to a combination of halo material , and not to distant Sculptor clouds based on a spatial and kinematic comparison between the Sculptor Group galaxies and the anomalous clouds , and the lack of cloud detection in the northern half of the group .
This result has significant implications for the hypothesis that there might exist distant , massive HVCs within the Local Group .
Cataloged clouds within the Magellanic Stream do not have a preferred scale size .
Their mass spectrum f ( M _ { HI } ) \propto M _ { HI } ^ { -2.0 } and column density spectrum f ( N _ { HI } ) \propto N _ { HI } ^ { -2.8 } are steep compared with Ly \alpha absorbers and galaxies , and similar to the anomalous clouds along the Sculptor Group sightline .